Circuit breaker blast valve mechanism



April 9, 1957 B. P. BAKER ETAL 2,788,191

CIRCUIT BREAKER BLAST VALVE MECHANISM Filed June 26, 1953 3 Sheets-Sheet l.

2a Fig.l..

' INVENTORS Benjamin P. Boker,woyne S.Aspey and Erling Frisch.

April 9, 1957 B. P. BAKER ET AL 2,788,191

CIRCUIT BREAKER BLAST VALVE MECHANISM Filed June 26, 1953 Fig.3.

Fig.4.

WITNESSES:

4%mz (7 D 5 Sheets-Sheet 3 Benjamin P.Boker,woyne $.Aspey 8nd Erling Frisch.

United States Patent 2,788,191 CIRCUIT BREAKER BLAST VALVE MECHANISM Benjamin P. Baker and Wayne S. Aspey, Turtle Creek, and Erling Frisch, Pittsburgh, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 26, 1953, Serial No. 364,452 11 Claims. (Cl. 251-35) This invention relates to valve mechanisms and more particularly to blast valve mechanisms designed for highspeed operation to supply compressed gas for operating the contacts and extinguishing the are drawn between the contacts of large circuit interrupters.

Modern circuit interrupters have been constructed for operation by fluid pressure, such as compressed air, and have been provided with means for separating the contacts and extinguishing the are drawn upon separation of the contacts comprising a blast valve mechanism operating at the proper instant to subject the contacts to a sudden blast of fluid under pressure.

A blast valve mechanism designed for such service must be adapted for high-speed operation since it is desirable to insure operation of the circuit breakers within a very small time interval. The blast valve mechanism must also be capable of high-speed closing in order to prevent excessive loss of fluid pressure, and should be operative to control the supply of fluid under a high pressure, which may be in the neighborhood of 350 pounds per square inch.

An object of the invention is to provide an improved blast valve mechanism capable of high-speed opening and closing operations.

Another object of the invention is to provide an improved highspeed, fluid-pressure-operated blast valve embodying a fluid-pressure-operated pilot valve for controlling the operation of the blast valve.

Another object of the invention is to provide an improved blast valve mechanism for a circuit interrupter comprising a main valve element, fluid pressure means for actuating the main valve element, a pilot valve and a sec ondary valve cooperating to elfect a sudden variation in the pressure of fluid on the fluid pressure means to effect high-speed operation of said main valve element and to prevent substantial loss of fluid pressure when the pilot valve is open.

The invention both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of a preferred embodiment thereof, when read in conjunction with the accompanying drawings.

In said drawings:

Figure 1 is a side elevation view of a circuit interrupter embodying the principles of the invention.

Fig. 2 is an enlarged sectional view of a portion of the circuit interrupter showing the arc extinguishing structure of the circuit interrupter and the blast valve mechanism.

Fig. 3 is an enlarged sectional view of the blast valve mechanism showing the blast valve in the closed position.

Fig. 4 is a view similar to Fig. 3, but showing the blast valve in the open position.

The invention is illustrated as applied to a circuit interrupter of the general type disclosed in copending application Serial No. 180,447, filed by Benjamin P. Baker, August 19, 1950, now Patent No. 2,644,876, issued July 7, 1953 and assigned to the assignee of the instant invention.

Referring to Fig. 1 of the drawings, the circuit interrupter is suitably supported on a base comprising a framework indicated generally at 11. Mounted on the framework 11 are tubular insulators 13 and 15 and a metal housing indicated generally at 17 is mounted on the upper end of the tubular insulator 15. A tubular insulator 19 mounted on the housing 17 supports a metal housing 21 which encloses the moving contact structure of the interrupter. Mounted on the metal housing 21 is a tubular insulator 23 which at is upper end supports a metal housing 25 enclosing an upper exhaust chamber and a metal cap 27 is mounted on the housing 25.

Suitably supported in the framework 11 is a compressedair tank or reservoir 29 having an elbow 31 secured to one end thereof upon which elbow is supported an insulating tube 33 which extends upwardly within the tubular insulators 13 and 15 and terminates below the housing 17. As shown in Fig. 2, the housing 17 is divided into two compartments, the lower compartment 35 comprising a high-pressure compartment and the upper one 37 comprising an exhaust compartment. A Y-shaped tube 39 (only one leg of which is shown) is connected to a cap 40 mounted on the upper end of the tube 33 and communicates with the high-pressure compartment 35. One of the legs of the tube 39 is disposed back of the blast valve mechanism, indicated generally at 41, and the other (not shown) communicates with the high pressure chamber in front of the blast valve mechanism.

The housing 17 for the high pressure chamber 35, the exhaust chamber 37 for enclosing the mechanism in the space just below the high pressure chamber comprises a base casting 43 (Figs. 1 and 2) mounted on top of the tubular insulator 15. A plate 45 is suitably secured, preferably by welding, on the casting 43 and plates 47 and 49 are secured to the plate 45 to form a box-like enclosure having cover members 51 (Figs. 1 and 2) removably mounted thereon for covering access openings. Mounted on the plates 4-7-49 is a plate 53 forming the bottom of the high-pressure chamber and a similar plate 55 forms the top of the high-pressure chamber. Side walls 57 mounted between the bottom disc 53 and the top disc 55 completes the high-pressure chamber.

The exhaust chamber 37 is formed by the plate 55 and a casting 59 having side members 61 mounted therebetween, the parts being secured preferably by welding. Integral with the casting 59 is a tubular extension 63 which extends downwardly into the exhaust chamber and disposed centrally within the tubular extension is a tubular divider 65 closed at its lower end and supported by means of a spider 67 integral with the casting 59 and with the divider 65. Openings 69 through the spider communicates the interior of the divider 65 with the exhaust chamber 37.

A tubular stationary contact member 71 threadedly engaging the upper end of the divider 65 has a stationary contact 73 mounted on the upper end thereof for cooperation with a lower movable contact member 75 disposed in the contact housing 21. An upper movable contact 77 also disposed in the contact housing 21 cooperates with an upper stationary contact 79 which is supported on an upper stationary contact member (not shown) like the contact member 71. The upper stationary contact member is housed in the tubular insulator 23 and terminates in the exhaust chamber 25. The arrangement of the upper stationary contact and the exhaust chamber 25 is the same as that for the cover contact except that it is inverted.

The movable contacts 75 and 77 are connected by a flexible conductor 81 and are pivotally supported respectively on the inner ends of links 83 and 85 by means of pivot pins 87 and 89. The outer ends of the links 83 and 85 are pivoted respectively on pivot pins 91 and 93- supported on a removable cover plate 95. The inner ends of the links 33 and 85 are connected by a toggle comprising toggle links 97 and 99 which are pivoted on the'pins-87 and 89'and pivotally connected together by aknee pivot pin 1191. A spring seat 193 is mounted on the knee pivotpin 101 and a coil spring 105 compressed between the spring seat 193 and the plate 95 biases the knee of the toggle 97-99 in a direction to extend the toggle, thereby applying contact pressure between the movable contacts 75 and 7? the corresponding stationary contacts 73 and 79. A spring guide 197 is provided on the plate 95 for guiding the spring 105.

The circuit through the interrupter extends from a line terminal 169 (Fig. 1) through the upper exhaust housing 25 and the upper stationary contact means (Fig. 2) including the upper stationary contact 79, the upper movable contact 77, the flexible conductor 81, the lower movable and stationary contacts 75, 73, lower contact member 71, the housing 17 (Fig. l), a shunt conductor 111, a disconnect switch comprising a support member 113 secured to the casting 43 by means of bolts (not shown), a disconnect switch blade 115, a stationary disconnect contact 117 and a line terminal 119.

The'support member 113 which is rigidly mounted on the casting 4-3 is also supported on a rotatable column comprising an insulator 121 and a member 123. The stationary disconnect contact 117 and the line terminal 119'are mounted on an insulator 125 supported on the general framework 11. Since the disconnect switch forms no part of the present invention, a detailed description thereof will not be given. It is believed suflicient to set forth that the switch is operated to the open position by means of a compressed gas operating mechanism indicated generally at- 127 which, when actuated, rotates the column 121-123 to eflect opening movement of the disconnect switch blade 115.

The blast valve mechanism for admitting a blast of compressed gas to blast the movable contacts open and extinguish the arc is mounted in a casing or cylinder 129 (Figs. 2, 3' and 4) disposed in central openings in the plates 53 and 55 and rigidly secured thereto preferably by welding. The upper end of the casing 129 abuts against the lower end of the extension 63 with a sealing gasi'et there'oetween to form a continuous passage. As best seen in Figs. 3 and 4 a cylindrical valve member 131 is removably mounted in a bore in the lower end of the cylinder 129 with the upper end thereof abutting a shoulder 133 in the bore of the cylinder 129. A member 135 disposed in the lower end of the bore of the cylinder 129 has a flange 137 thereon closely fitting in the bore of the cylinder 129 at the lower end of the valve member 131. The member 135 and the valve member 131 are held in place by an annular member 139 having a cylindrical extension 141 cooperating with the flange 137 of the member with a sealing gasket therebetween. The annular member 139 is provided with a flange 143 and. is secured to the enlarged lower end of the cylinder 129 by means of a series of bolts 145 passing through openings in the flange 143 and threaded into tapped openings in the end of the cylinder 129.

A valve seat 147 integral with the upper end of the cylindrical valve member 131-cooperates with a blast valve 149 on the upper end of a valve piston or abutment 151 slidably mounted in the bore of the valve element 131. The valve piston or abutment 151 is in the shape of an inverted cup and together with the valve element 131 forms a chamber 152 below the abutment. A central tubular extension 153 extends downward from the upper portion of the valve piston and has a bore 154 therein. Slidable in the bore 154 of the tubular extension 153 'is a' secondary valve 155 having a central passage 156itherethrough and having a flange157 supported by a spider integral with the lower end of the secondary valve" 155'. A compression spring 159' dis- 4. posed between the abutment 151 and the flange 157 of the secondary valve biases the blast valve 149 closed and biases the flange 157 into engagement with an inner flange 161 on the member 135.

A pilot valve 163 normally engaging a valve seat 165 is mounted on the upper end of a-valve stem 167 slidably mounted in a valve guide 169. The valve guide 169 forms the center portion of a spider 171 which is secured to the valve seat 165 by screw bolts 173 (only one being shown) and both the spider 171 and the valve seat are secured in a counter bore in the bottom of the member 135 by means of screw bolts 175 (only one being shown). A coil spring 177 compressed between the lower side of the spider 171 and a washer 179 seated against a nut 131 threaded onto the lower portion of the valve stem 157 biases the pilot valve 163 into engagement with the valve seat 165, thus closing off the central passage through the valve seat.

By removing the bolts 145 and disconnecting a link 185, the entire blast valve device including the cylindrical valve member 131 may be removed from the cylinder 129 for inspection or repairs.

In order to operate the pilot'valve 163 to effect opening of the blast valve 149, a member 153 threaded onto the lower end of the valve stem 167 has its lower end bifurcated to receive the upper end of the link which is pivotally connected to the member 183 by means of a pivot pin 187. The'lower end of the link 185 is pivotally connected by means of a pivot pin 189 to one end of a lever 191 pivotally supported between its ends by a pivot pin 193 mounted in a bracket 195 (Fig. 2) secured to the cap' 49 preferably by welding. Pivotally connected to the other end of the lever 191 by means of a pivot pin 197 is the upper end of an insulating operating rod 199 having a piston 201 (Fig. 1) connected to the lower end thereof. The piston 291 is disposed in a cylinder 203 supported on the framework 11 by means of brackets2t 5.

Compressed gas is admitted to the cylinder 203 above the piston 291m operate the rod 199 and the pilot valve 163 by means of a valve mechanism indicated generally at 207, operated by an electromagnet 209. The valve mechanism is connected to the reservoir 29 by means of a pipe 211. The valve mechanism is of a well-known type which in the closed position shuts off a passage for admitting compressed gas to the operating cylinder on the working side of the piston and opens a passage which vents the cylinder on the working side of the piston to atmosphere. When operated by the electromagnet, the valve closes off the vent to atmosphere and opens the passage to admit compressed gas to the cylinder on the working side of the piston to operate the piston.

The blast valve is of the balanced pressure type and is operated to open position by unbalancing the pressure on one side thereof. In orderto balance the pressure on both sides of the abutment 151, compressed gas is admitted from the high-pressurechamber 35 (Fig. 2) to the space below the closed end of the valve piston 151 through several inlet passages 213 (Figs. 2, 3 and-4) in the cylinder 129, a plurality of restricted radial passages 215 in 'an'annular groove 216 in the blast valve, through the tubular extension 153 and the hollow stem of the secondary valve 155 to the space below the abutment 151.

When the electromagnet 299 (Fig. l) is energized, it operates the valve device 207 to admit compressed gas to the cylinder 293' above the piston 2G1 moving the piston 2191 and the operating rod 199 downward. This rocks the lever 191 (Figs. 2-and 3) clockwise and uneats the secondary valve 153 dumping the compressed gasfr'om below the abutment 151. At the same time, the ope-ningmovement of the pilot valve 163 causes the spherical upper face of this valve to engage the valve seatat the lower end of the tubular secondary valve 155 closing oi the passage 1561 and slightly raising the flange 157 from the flange 151. Operation of the secpiston 151 to quickly come into balance.

' ondary valve closes the passage 156 shutting off. the highpressure gas from the space below the piston 151 and dumps the high-pressure gas from below the piston to atmosphere, whereupon the high-pressure gas above the piston 151 blasts the piston downwardly opening the large passage through the blast valve seat 147 and adv mittinga blast of high-pressure gas upwardly through the cylinder 129, through the passages around the divider 65 and through the space between the stationary contact member 71 and the inner wall of the tubular insulator 19 to the space around the lower stationary contact 73 and lower movable contact 75. The blast of high-pressure gas flows through passages 217 (Fig. 2) past the contact housing 21 to the space around the upper movable and stationary contacts 7779. The high-pressure gas blasts the movable contacts 7577 inwardly to the open position against a stop member 223 mounted on and extending inwardly from cover member 225 secured to the housing 21. The high-pressure gas then flows through openings 219 and 221 respectively in the lower and upper stationary contacts 77 and 7 9 extinguishing the arc and then passing downwardly through the interior of the tubular stationary contact 71 and through the openings 69 into the exhaust chamber 37. The

' upper stationary contact 79 is mounted on a tubular contact member (not shown)lil e the contact member 71 except that it is inverted and the compressed gas flows upwardly through the tubular contact member into an upper exhaust chamber indicated at (Fig. l). The shock of the high-speed opening movement of the blast valve piston 151 is absorbed by a plurality of spring washers 226.

The compressed gas is not immediately dumped from the exhaust chamber 37. A dump valve indicated generally at 227 (Fig. 2) is provided to control the dumping of the compressed gas from the exhaust chamber, but this dump valve is prevented from functioning until the blast valve closes. The dump valve 227 comprises a valve housing 229 having a threaded portion 231 threaded into, a tapped opening 233 in the annular member 61. A piston valve 235 disposed in the bore of the housing 229 is biased closed by a spring 237 to normally close off an exhaust port 239 in the housing 229. The construction of the valve member 235 is such that compressed gas in the exhaust chamber 37 will blast the exhaust valve open, however, means is provided operative upon opening a of the pilot valve 163 to supply high-pressure gas from the high-pressure chamber to the space above the ,piston valve 235 to prevent opening movement of the. valve until the pilot valve 163 closes to effect closure of the blast valve.

The pilot valve 163 is closed by the spring 177 (Figs.

. 2, 3 and 4) upon deenergization of the electromagnet .209 (Fig. 1). When the magnet 209 is deenergized, the valve device 207 closes off the compressed gas from the cylinder 203 whereupon the spring 177 closes the valve 163 and rocks the lever 191 (Fig. 2) counter-clockwise raising theoperating rod 199. When the pilot valve 163 closes, it opens the passage 156 through the secondary valve 155 permitting the pressure above and below the As soon as the pressure above and below the piston 131 is balanced, the spring 159 snaps the piston 131 upwardly to quickly close the blast valve.

The means for supplying gas pressure above the piston valve 235 (Fig. 2) comprises a valve device indicated generally at 241 (Fig. 2). The valve device includes a .housing 243 having a bore 245 therein in which is disposed a piston valve 247 which is operated to open and closed positions bythe movement of the operating rod 199 through the agency of a piston rod 249. When'the mechanism is in the normal position with the pilot valve 163 closed, the piston valve 247 is iuthe upper position as shown, in which position the valve 247 closes a passage 251 in the housing 243. One end of the passage 251 is connected by means of a pipe 253 to the high-pressure chamber 35 and the other end of the passage 251 is connected to the space in the housing 229 above the dump valve piston 235 by a pipe 255. Thus the piston valve 247 normally closes off the passage 251 and at the same time opens an exhaust passage 257 which communicates the pipe 255 and hence the space above the dump valve 235 to atmosphere.

When the electromagnet 209 (Fig. 1) is energized to effect downward movement of the operating rod 199 and opening of the pilot valve 163 to initiate opening of the blast valve, the piston valve 247 (Fig. 2) is moved downward to close the exhaust passage 257 and open the passage 251. Compressed gas is thereby admitted to the dump valve 227 to hold the valve closed until the mechanism is operated to effect closure of the blast valve.

When the electromagnet 209 (Fig. 1) is deenergized to permit closure of the pilot valve 163 (Fig. 2) the rod 199 is moved upwardly moving the valve 247 upwardly to its normal position. This shuts off the flow of pressure to the dump valve 227 and vents the pressure from above the valve member 235 to atmosphere through the exhaust passage 257. The high-pressure gas in the exhaust chamber 37 then blasts the valve 235 open and clumps the pressure from the exhaust chamber 37, the space around the movable contacts and above the blast valve to atmosphere. When the pressure adjacent the movable contacts 75-77 falls below a predetermined level the spring 195 acts to move the contacts 7577 to the closed position. Also, when the pressure in the exhaust chamber 37 falls to a predetermined level the spring 237 closes the dump valve 235.

A dump valve 227 (Fig. 1) is provided for dumping the compressed gas from the upper exhaust chamber 25. The upper dump valve 227 is exactly like the lower dump valve and is controlled by high-pressure gas admitted thereto by the valve device 243 (Fig. 2) through the pipe 255 and an insulating pipe 2559 (Figs. 1 and 2).

The invention provides a high-speed air blast valve mechanism for a circuit interrupter that is removable as a unit for inspection and/or repairs. The blast valve is grooved or undercut just below the valve portion to provide a slight flexibility to the outer portion of the valve element which engages the valve seat making an airtight seal. The valve mechanism uses a common spring for biasing the blast valve closed and for providing seat 'ing pressure between the pilot valve and the movable secondary valve. The movable secondary valve cooperating with the pilot valve to provide high-speed closing of the blast valve and also prevents loss of compressed gas when the the blast valve is in the open position.

Having described the invention in accordance with the requirements of the patent statutes, it is to be understood that various changes and modifications may be made in the structure details thereof without departing from some of the essential features of the invention.

We claim as our invention:

1. In a circuit interrupter having separable contact means and means for directing a blast of fluid under pressure toward said contact means for separating said contact means and for extinguishing the are drawn during separation thereof, a blast valve device having an inlet passage and a discharge passage, blast valve means for controlling the flow of fluid under pressure from said inlet passage to said outlet passage, a movable abutment operative by the fluid pressure from said inlet passage for actuating said blast valve means, a tubular extension on said abutment, a secondary tubular valve slidably engaging said tubular extension to form passage means communicating said inlet passage with the space on the opposite side of said abutment for balancing the pressure on both sides of said abutment, a normally closed pilot valve controlling an exhaust port from said space on said opposite side of said abutment, means for operating said pilot valve to open position to suddenly unbalance the pressure on one side of said abutment to effect opening movement of said blast valve means, and said pilot valve when moved to said open position engaging said :secondary valve to close off said passage means.

2. In a circuit interrupter having separable contact means and means for directing a blast of fluid under pressure toward said contact means for separating said contact means and for extinguishing the arc drawn during separation thereof, a blast valve device having an inlet passage and a discharge passage, blast valve means for controlling the flow of fluid under pressure from said inlet passage to said outlet passage, a movable abutment operative by the fluid pressure from said inlet passage for actuating said blast valve means, a tubular extension on said abutment, a secondary tubular valve slidably engaging said tubular extension to form passage means communicating said inlet passage with the space on the opposite side of said abutment for balancing the pressure on both sides of said abutment, spring means compressed between said abutment and said secondary valve biasing said blast valve closed and biasing said secondary valve to a predetermined position, a normally closed pilot valve controlling an exhaust port from said space on said opposite side of said abutment, means for operating said pilot valve to open position to suddenly unbalance the pressure on one side of said abutment to effect opening movement of said blast valve means, and said pilot valve when moved to said opening position engaging said secondary valve to close off said passage means.

3. In a circuit interrupter having separable contact means and means for directing a blast of fluid under pressure toward said contact means for separating said contact means and for extinguishing the arc drawn during separation thereof, a blast valve device having an inlet passage and a discharge passage, blast valve means for controlling the flow of fluid under pressure from said inlet passage to said outlet passage, a movable abutment operative by the fluid pressure from said inlet passage for actuating said blast valve means, a tubular extension on said abutment, a secondary tubular valve slidably engaging said tubular extension to form passage means communicating said inlet passage with the space on the opposite side of said abutment for balancing the pressure on both sides of said abutment, spring means compressed between said abutment and said secondary valve biasing said blast valve closed and biasing said secondary valve to a predetermined position, a normally closed pilot valve controlling an exhaust port from said space on said opposite side of said abutment, means for operating said pilot valve to open position to suddenly unbalance the pressure on one side of said abutment to effect opening moveent of said blast valve means, and said pilot valve when moved to said open position engaging said secondary valve to close off said passage means, and housing said secondary valve so that said spring applies pressure between said secondary valve and said pilot valve.

4. A blast valve mechanism for a circuit breaker comprising a casing structure having an inlet passage and a discharge passage, blast valve means mounted in said casing for controlling communication from said inlet passage to said discharge passage, fluid pressure responsive means for operating said blast valve means, a tubular secondary valve member slidably engaging said fluid pressure responsive means to form a communication from said inlet passage to the opposite side of said fluid pressure responsive means for equalizing the pressure of fluid on both sides of said fluid pressure responsive means, a normally closed pilot valve operable to open position for suddenly varying the pressure of fluid on said fluid pressure responsive means, means for operating said pilot valve to said open position, and said pilot valve when moved to said open position engaging said tubular secondary valve member t9 close the communication from said inlet passage to the opposite side of said fluid pressure responsive means.

5. A blast valve mechanism comprising a casing structure having an inlet passage and a discharge passage, blast valve means mounted in said casing for controlling communication from said inlet passage to said discharge passage, fluid pressure responsive means for operating said blast valve means, normally open secondary valve means for controlling communication from said inlet passage to the opposite side of said fluid pressure responsive means for equalizing the pressure of fluid on both sides of said fluid pressure responsive means, spring means disposed between said fluid pressure responsive means and said secondary valve means biasing said blast valve means closed and biasing said secondary valve means against a fixed stop means, a normally closed pilot valve controlling an exhaust port from said space on said opposite side of said pressure responsive means operable to open position for suddenly varying the pressure of fluid on said fluid pressure responsive means, means for operating said pilot valve to said open position, and said pilot valve when moved to said open position engaging said secondary valve means to close the communication from said inlet passage to the opposite side of said fluid pressure responsive means, and moving said secondary valve means away from said fixed stop means so that said spring means applies a pressure between said secondary valve means and said pilot valve.

6. A blast valve mechanism comprising a casing structure having an inlet passage and a discharge passage, blast valve means mounted in said casing for controlling communication from said inlet passage to said discharge passage, fluid pressure responsive means for operating said blast valve means, means defining a passage communicating said inlet passage with the space on the opposite side of said fluid pressure responsive means from said inlet passage, a normally closed pilot valve operable to open position for suddenly varying the fluid pressure on said fluid pressure responsive means, a tubular secondary valve member forming part of said passage disposed between said fluid pressure responsive means and said pilot valve and slidably engaging said passage means, means for operating said pilot valve to open position, said pilot valve when operated to said open position moving relative to and engaging said tubular secondary valve memher to close said passage means.

7. A blast valve mechanism comprising a casing structure having an inlet passage and a discharge passage, blast valve means removably mounted in said casing structure for controlling communication from said inlet passage to said discharge passage, a movable abutment responsive to fluid pressure from said inlet passage for actuating said blast valve means, normally closed pilot valve means for controlling the pressure of fluid on said movable abutment, a tubular secondary valve member slidably engaging said movable abutment to form a passage communicating the opposite sides of said abutment and coacting with said pilot valve means to control the pressure of fluid on said movable abutment, actuating means for moving said pilot valve means to open position, and said pilot valve means during its opening movement engaging and closing said tubular secondary valve member.

8. A blast valve mechanism comprising a casing structure having an inlet passage and a discharge passage, blast valve means mounted in said casing structure for controlling communication from said inlet passage to said discharge passage, a movable abutment disposed in said casing structure and responsive to fluid pressure from said inlet passage for actuating said blast valve means, normally closed pilot valve means disposed coaxially with said movable abutment for controlling the pressure of fluid on said movable abutment, a tubular secondary valve member slidably engaging said movable abutment and coacting therewith to form a passage communicating opposite sides of said abutment, means for moving said pilot valve means to open position, and said pilot valve means during the opening movement thereof engaging said secondary valve member to close said passage to thereby eflect a suddent variation of fluid pressure on said abutment.

9. A blast valve mechanism comprising a casing structure having an inlet passage and a discharge passage, blast valve means mounted in said casing structure for controlling communication from said inlet passage to said discharge passage, a movable abutment disposed in said casing structure and responsive to fluid pressure from said inlet passage for actuating said blast valve means, normally closed pilot valve means disposed coaxially with said movable abutment for controlling the pressure of fluid on said movable abutment, a tubular secondary valve member disposed coaXially with said movable abutment and coacting therewith to provide a passage communicating opposite sides of said abutment, spring means compressed between said movable abutment and said tubular secondary valve means biasing said blast valve means closed and biasing said secondary valve means against a fixed stop, means for moving said pilot valve means to open position, and said pilot valve means during the opening movement thereof engaging said tubular secondary valve member to close said passage to thereby eifect a sudden variation of fluid pressure on said abutment.

10. A blast valve mechanism comprising a casing structure having an inlet passage and a discharge passage, blast valve means mounted in said casing structure for controlling communication from said inlet passage to said discharge passage, a movable abutment disposed in said casing structure and responsive to fluid pressure from said inlet passage for actuating said blast valve means, normally closed pilot valve means disposed coaxially with said movable abutment for controlling the pressure of fluid on said movable abutment, secondary tubular valve means disposed coaxially with said movable abutment and coacting therewith to provide a passage communicating opposite sides of said abutment, spring means biasing said secondary valve means to a predetermined position, means for moving said pilot valve means to open position, and said pilot valve means during the opening movement thereof engaging said secondary tubular valve means to close said passage to thereby effect a sudden variation of fluid pressure on said abutment, said pilot valve means when moved to open position moving said secondary valve means away from said predetermined position so that said spring means applies a pressure between said secondary valve means and said pilot valve means.

11. In a blast valve mechanism for a circuit interrupter, the combination of a casing structure having an inlet passage supplied with fluid under pressure, a discharge passage, and a chamber in said casing structure, a main valve disposed in said casing for controlling the flow of fluid under pressure from said inlet passage to said discharge passage, a movable abutment disposed between said inlet passage and said chamber for operating said main valve, means defining a relatively large passage for admitting fluid under pressure from said inlet passage to said chamber, pilot valve automatically operative to vent fluid under pressure from said chamber to initiate operation of said main valve by said movable abutment, and a tubular valve member disposed in said chamber slidably engaging a portion of said abutment to form said relatively large passage and engaged by said pilot valve to close said relatively large passage while said pilot valve is in the open position.

References Cited in the file of this patent UNITED STATES PATENTS 534,514 Mellin Feb. 19, 1895 1,368,208 Flynn Feb. 8, 1921 1,654,602 Reynolds Ian. 3, 1928 2,672,887 Tipton Mar. 23, 1954 

